EL 4 - Inorganic Chemistry and the Periodic Table

Question 1

What is first ionisation enthalpy?

Answer 1

The enthalpy change that occurs when one mole of electrons is removed from one mole of gaseous atoms

Question 2

What does the group (column) number represent in the periodic table?

Answer 2

The group number represents the number of electrons present in the outer shell of the atom

Question 3

What does the period (row number) represent in the periodic table?

Answer 3

The period represents the number of electron shells in the atom

Question 4

Why does first ionisation increase as we move across a period?

Answer 4

The number of protons in the nucleus increases which increases the nuclear charge and thus the nuclear force felt by outer electrons it therefore takes more energy to remove them

Question 5

What is the formula of a nitrate ion?

Answer 5

NO3 -

Question 6

What is the formula of a sulfate ion?

Answer 6

SO4 2-

Question 7

What is the formula of a carbonate ion?

Answer 7

CO3 2-

Question 8

What is the formula of a hydroxide ion?

Answer 8

OH -

Question 9

What is the formula of an ammonium ion?

Answer 9

NH4 +

Question 10

What is the formula of a hydrogencarbonate ion?

Answer 10

HCO3 -

Question 11

What is the formula of a copper ion?

Answer 11

Cu 2+

Question 12

What is the formula of a zinc ion?

Answer 12

Zn 2+

Question 13

What is the formula of a lead ion?

Answer 13

Pb 2+

Question 14

What is the formula of an Iron (II) ion?

Answer 14

Fe 2+

Question 15

What is the formula of an Iron (III) ion?

Answer 15

Fe 3+

Question 16

Why does the first ionisation energy decrease down a group?

Answer 16

The number of shells in the atom increases, which increases the shielding of outer electrons from the nucleus. The nuclear radius also increases. Both of these factors mean that the attractive nuclear force felt by the electron is smaller, so it takes less energy to remove outer electrons

Question 17

How do the charge densities of group 2 ions affect the thermal stability of their carbonates?

Answer 17

Smaller ions with the same charge have higher charge densities and distort the carbonate ion, so that the compound will decompose at a lower temperature

Question 18

How can we test for Fe 2+ ions?

Answer 18

Add OH- ions, the green solution will form a green precipitate

Question 19

How can we test for Fe 3+ ions?

Answer 19

Add OH- ions, the yellow solution will form an orange precipitate

Question 20

How can we test for Cu 2+ ions?

Answer 20

Add OH- ions, the blue solution will form a blue precipitate

Question 21

How can we test for NH4 + ions?

Answer 21

Add NaOH(aq) to a boiling tube containing the NH4 + ions, warm the boiling tube. Any vapours given off by the tube will turn damp red litmus paper blue if NH4 + ions are present

Question 22

How can we test for Al 3+ ions?

Answer 22

Add OH- ions, the colourless solution will form a white precipitate

Question 23

How can we test for Cl- ions?

Answer 23

Add a few drops of HNO3, shake the test tube. Add a few drops of AgNO3, a white precipitate should form

Question 24

How can we test for Br- ions?

Answer 24

Add a few drops of HNO3, shake the test tube. Add a few drops of AgNO3, a cream precipitate should form

Question 25

How can we test for I- ions?

Answer 25

Add a few drops of HNO3, shake the test tube. Add a few drops of AgNO3, a yellow precipitate should form

Question 26

How can we test for SO4 2- ions?

Answer 26

Add Ba 2+ ions, a white precipitate should form

Question 27

How can we test for CO3 2- ions?

Answer 27

Add dilute nitric acid, if effervescence occurs then CO3 2- ions are present

Question 28

How can we test for Li+, Na+, K+ and Ca+ ions?

Answer 28

Evaporate the water from the sample, moisten a test wire and collect the solid residue from the evaporating dish. Pass this residue into a bunsen burner and record the colour of the flame

Question 29

Which ions show which colours in the flame test?

Answer 29

Na+ = Orange
Ca+ = Brick red
Li+ = Red
K+ = Lilac
Ba 2+ = Green
Cu 2+ = Blue-green

Question 30

How can we test for Pb 2+ ions?

Answer 30

Add OH- ions, a white precipitate will form. Upon adding excess OH- ions, the precipitate will dissolve